In the early 1980's the automotive industry began to switch production from rear wheel drive vehicles to front wheel drive vehicles. Generally, front wheel drive passenger vehicles are now more common than rear wheel drive vehicles. This change resulted in a significant redesign of vehicle drive systems. Today, front wheel drive vehicles typically have two driveaxles, one to connect each front wheel with the vehicle transmission. In four wheel drive and independent rear suspension vehicles the automobile can have four driveaxles. Each driveaxle typically requires two constant velocity (CV) joints, a type of universal joint, to allow for movement of the driveaxles in relation to the transmission as the vehicle wheels encounter uneven terrain.
Because of the proximity of the CV joints to a highway or road, CV joints require a flexible `boot`, which is attached over the joint to protect it from stones, debris and other external contaminants while retaining lubricants and maintaining integrity of the precision internal bearing surfaces of the CV joint. It is well known in the prior art to use band clamps for the attachment of boots to CV joints, and crimp-style clamps have been the preferred means for attaching boots for the past decade. Crimp-style clamps have an outwardly projecting deformable crimp lug by which the clamp is installed, as described in U.S. Pat. No. 5,105,509. This method is favoured for its simplicity as a mechanical means to retain and seal the boot to the CV joint.
More recently, anti-lock braking systems (ABS) have been installed on vehicles to provide improved vehicle braking. Originally, such a safety device was mainly installed in higher priced vehicles, but ABS is now becoming a standard installation on many vehicles. On front wheel drive vehicles, anti-lock braking systems have an ABS wheel position ring encircling the CV joint adjacent the wheel, and an ABS sensor suspended from the vehicle chassis mounted proximate the position ring so as monitor wheel rotation. This location is disadvantageous as it is typically adjacent the crimp-style clamp affixing the boot. The positioning of the ABS sensor greatly reduces the amount of radial clearance available around the CV joint to which the crimp-style clamp is installed, creating a risk of interference between the crimped clamp and the ABS sensor. Such interference can damage the sensor during wheel rotation while the vehicle is operating. Similarly, affixing a crimp style clamp during a repair of the vehicle could result in inadvertent damage to the sensor and render the ABS inoperative.
The reduced clearance necessary for the ABS sensor has forced the development of lower profile crimps on crimp-style clamps. For example, Canadian Patent No. 1,286,094 discloses an earless or lugless clamp structure. However, at the original equipment manufacturer (O.E.M.) level these lower profile crimp style clamps can be only utilized when softer boot compounds are used, due to their inherent lower crimping loads. Generally, the use of a clamp results in greater complexity and cost in the assembly of the vehicle, and raise the likelihood of damage to the ABS sensor during replacement.
A further disadvantage to the use of clamps to affix boots to CV Joints has arisen due to new materials now used to manufacture boots. It is well known in the art to mould boots from neoprene, however, it has been determined that neoprene is susceptible to damage from heat from the vehicle's engine, which can lead to premature deterioration of the boot Silicone has also been commonly used, but more recently, Hytrel.RTM., a product of Dupont Chemical Inc. is being used for its superior resilience to vehicle engine heat and imperviousness to debris and other environmental contaminants present on highways and other vehicle driving surfaces. While Hytrel.RTM. is proving to be a superior material for CV boots, it's properties require a high pressure to adequately secure the boot to the CV joint. Thus, in order to provide low profile clamps with sufficient crimping pressure, it is now commonplace to use a swage ring or compression ring as described in U.S. Pat. No. 5,768,752, which further increases the complexity of vehicle design and assembly.
It will be apparent that other universal joints can suffer from some of the foregoing disadvantages. For example, the rack and pinion steering unit universal joint is also located near to the vehicle driving surface, thereby necessitating a protective boot.